<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>

    <!--响应式设置-->
    <meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1, user-scalable=no">
    <!--加入外部样式-->
    <link rel="stylesheet" href="css/bootstrap.css">
    <!--加入jQuery的框架-->
    <script src="js/jquery-3.6.1.js"></script>
    <!--加载b3脚本-->
    <script src="js/bootstrap.js"></script>
</head>
<body>

    <h1><a id="a1" href="javascript:void(0)">a1</a> &nbsp;&nbsp; <a id="a2" href="javascript:void(0)">a2</a> &nbsp;&nbsp; <a id="a3" href="a3.html" target="workarea">a2</a></h1>

    <iframe name="workarea" style="border-width: 0px; width: 100%; height: 100%;"></iframe>

</body>
</html>

<script>
    $("#a1").click(function () {
        window.open("a1.html", "workarea");
    });
    $("#a2").click(function () {
        window.open("a2.html", "workarea");
    });
</script>